Polymerizable compositions are used in a wide variety of applications. For chemical curing systems, the polymerizable compositions advantageously comprise a two-paste system where the pastes are mixed immediately before use. Mixing of the two pastes initiates a chemical reaction that results in a cured material. Addition-curable silicones, for example, exhibit fast curing speeds and low shrinkages, and typically use a platinum-containing hydrosilation catalyst. This type of catalyst necessitates the use of vinyl-functionalized silicon-containing oligomers, which are generally expensive. In addition, there may be undesirable hydrogen evolution from the decomposition of the hydrosiloxane cross-linkers that are present in these systems.
Another type of polymerization system has been recently developed, wherein curing is achieved by a ring-opening metathesis polymerization (ROMP) mechanism. Metathesis is generally understood to mean the metal catalyzed redistribution of carbon-carbon double bonds. The polymerizable composition comprises a resin system that includes functionalities or groups that are curable by ROMP together with a metathesis catalyst, such as a ruthenium carbene complex. Usually the most expensive component of a ROMP curable formulation is the metathesis catalyst. There exists a need for increasing the efficiency of the metathesis catalyst in order to reduce costs and improve control for the speed of the polymerization process. Because the ROMP system is relatively new, there still exists a need to develop polymerizable compositions that cure efficiently by this metathesis reaction.
In addition to ROMP, other metathesis reaction systems utilize metathesis catalysts, for example ring closing metathesis, acyclic diene metathesis polymerization, ring opening metathesis and cross metathesis. There is further a need for increasing the efficiency of the metathesis catalyst in these other metathesis reaction systems.